Components of a “parasite – host” system

A "parasite-host" system consists of two main components:

1. Parasite: This is an organism that lives on or in a host organism and gets its food from or at the expense of its host. There are several types of parasites, including protozoa, arthropods, bacteria, and viruses. Parasites can cause disease in humans. Some parasitic diseases are easily treated and some are not.

2. Host: This is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In a parasite-host relationship, the host always suffers some degree of harm. The host can be a human, animal, or plant.

The interaction between the parasite and the host is a dynamic process with the balance of survival for the parasite and the degree of harm to the host being delicately balanced. The host's immune system plays a significant role in this balance, often determining the outcome of the interaction.